Air inlet flap

ABSTRACT

A series of inlet fences or spoilers carried on the nacelle of an aircraft turbine engine which are used to selectively divert streamlines which would otherwise become detached at the inlet lip. This selectively variable air-inlet geometry provides for minimum drag during cruise and yet obviates engine surge or stall or other effects detrimental to the engine which could otherwise occur on the ground and at low forward velocity when crosswinds combine with high engine power demands.

United StateS Patent 11 1 UNITED STATES PATENTS 3/1972 Sans et a]. 244/5 3 B Traksel et al. Nov. 6, 1973 [5 AIR INLET FLAP 3,059,878 ll/l962 Kerry et al. 244 53 B I {75] Inventors: Johan Trakselchatsworth; Joseph 2,539,089 l/ l95l Lear 244/53 R D. Dupcak, Studio City, both of I Calif. Pr1mary ExammerGeorge E. A. Halvosa Assistant Examiner-Edward R. Kazenske [73] Assigneez Lockheed Aircraft Corporation, Attorney george Sumvan e 3] Burbank, Calif,

. [22] Filed: Dec. 8, 1971 571 I ABSTRACT PP' 205,882 A series of inlet fences or spoilers carried on the nucelle of an aircraft turbine engine which are used to se- 52 us. (:1. 244/53 B, 137/151 lechvely divc" Streamlines which Wu|d 51 Int. Cl B64d 29/00 detached at the inlet P- This selecively variable 58 Field of Search 244/53 R, 53 B, 42 CA, air-inlet geometry p c f minimum g during 244/42 A 42 D 42 CD, '42 1 7 5 5 cruise and yet obviates engine surge or stall or other effects detrimental to the engine which could otherwise [56] Reerences Cited occur on the ground and at low forward velocity when crosswinds combine with high engine power demands.

10 Claims, 7 Drawing Figures SHEETIHFZ JOHAN TRAKSEL JOSEPH D. DU PCAK INVIENTOKS.

Agent 1 AltNTED 51973 SHEET 2 [IF 2 JOHAN TRAKSEL JOSEPH D. DUPCAK INVENTORS.

Agents AIR INLET FLAP BACKGROUND OF THE INVENTION Prior Art Heretofore there have been employed various means to control air distribution to the inlet of an aircraft turbine engine under both static and dynamic operating conditions. Most commonly used means for air inlet control are complex blow-in doors. A disadvantage of such doors is that they require a sharp bend or diversion in the'air flow and therefore result in poor air'distribution. The doors also allow for noise to be radiated to the side. Another technique to improve static performance is shown in U.S. Pat. No. 2,948,111 to Nelson, wherein there is described an inflatable means for changing the inlet lip geometry. However, the structural aspects of prior designs and poor performance have precluded their. commercial acceptance.

SUMMARY OF THE INVENTION an effective fence whereby the airstream flowing over the engine nacelle is diverted to cause a desirable change in the flow of inlet air at the lip. This arrangement enables high-performance engine air inlets, of the type designed for high-speed level flight, to be satisfactorily operated statically and at low forward speed in high crosswinds without inducing unacceptable flow distortion at theengine inlet face. Also, the design of the present invention lends itself to be economically retrofitted intoexisting designs in order to improve static and vcrosswind performance.

' The spoiler mechanism of the invention should not be confused with spoilers'or lift control devices of the type disclosed in U.S. Pat. Nos. 2,503,585 or 2,948,111 which are concerned with mechanisms for controlling the effective lift of the aircraft.

It is, therefore, an object of the invention to provide novel and improved inlet flaps, spoilers, or the like which allows the inlet design to be optimized for highspeed cruise conditions while still allowing satisfactory engine operation under static conditions, particularly in' adverse cross-wind conditions.

Another object of the invention is to provide a novel and improved means for overcoming undesirable flow separation of the airflow pattern at the inlet of a turbine engine which could otherwise result in a deterioration of engine performance.

Another object of the invention is to provide a novel These and other objects of the invention will become more readily apparent upon consideration of the following specification and the described drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG I is a perspective view of a turbine engine having the features of the instant invention incorporated therein and with the fence device shown in its retracted condition.

FIG. 2 illustrates the apparatus of FIG. I with the fence device in its extended position.

FIG. 3 is a schematic diagram of the lip portion of a turbine engine inlet illustrating the aerodynamic flow thereabout under a first operating condition.

FIG. 4 is a view similar to FIG. 3 illustrating air flow under an alternate operating condition.

FIG. 5 is a view similar to FIGS. 3 and 4, illustrating the inlet fence of the invention in an extended configuration. I

FIG. 6 is a fragmentary view, in cross' section, illus trating the operating mechanism for selectively controlling the position of the inlet fence. v

FIG. 7 is a view similar to FIG. 6 illustrating the mechanism in an extended position.

DESCRIPTION OFTHE PREFERRED I EMBODIMENT forward lip 3 thereof is a series of aerodynamic flaps or petal-like spoilers, a typical one of which is identified at 4. These flaps 4 are shown in the retracted position in FIG. 1, wherein they interpose no obstacle to the flow of air over the lip 3 and cowling 2. The retracted position shown in FIG. 1 is the preferred operating condition for normal engine operation, and as would be encountered during the cruise phase of an aircraft flight.

The flaps 4 may be selectively actuated so as to move them into an extended position as shown in FIG. 2. In this condition the flaps 4 are essentially perpendicular to the exterior surface of the nacelle l at the base of the flaps 4. This effectively alters the aerodynamic characteristics of the lip shape in order to force the air flow to provide the desired inflow condition. A more detailed explanation of the airflow characteristics under the two operating conditions will be given hereinafter in conjunction with the description of FIGS. 3-5. It should be understood that the distance between the leading edge of lip 3 and the mounting locating of the circumferential flaps 4 is at a predetemiined location with respect to the longitudinal axis of the engine, and extends outwardly (viz, radially) a predetermined distance into the surrounding air flow. Both the axial location and the degree of extension into the air flow stream depends upon the shape and size of the inlet and lip of the engine cowling, as well as the inlets operational requirements.

Although FIGS. 1 and 2 illustrate a fence that is disposed substantially all of the way aroundthe periphery of the engine cowling, it should be understood that the extent to which the flaps extend circumferentially may be reduced to conform with the desired aerodynamic characteristics of avparticular installation, and to accomodate various kinds of inlet shape or nacelle geometry or location on the airplane. Thatis, the fence can be restricted in an arcuate dimension from essentially zero to the full 360 circumference of the nacelle, and need not necessarily be continuous.

The flaps 4 shown in FIGS. 1 and 2 can be either solid or perforated to permit controlled leakage of the air flow. Any suitable mechanism can be employed to selectively extend and retract the flaps whether by automatic control or in response to a manually instituted command.

While it is preferred that the flaps comprising the fence extend outwardly from the surface of the nacelle so as to be substantially perpendicularly therefrom, if desired the flaps may be directed outwardly at an angle either towards or away from the inlet end of the engine.

There is diagrammatically shown in FIG. 3 a typical air flow pattern around the inlet lip during static operation in a crosswind. As a result of the lip geometry, the flow has a tendency to separate as indicated at for certain combinations of inlet velocity and crosswind velocity. To overcome this undesirable flow separation it becomes necessary to controllably alter the airflow pattern. Depending upon the operational requirementsof the aircraft, which have to be met at the low end of the speed regime, a lip shape of the type shown in FIG. 4 can be constructed which will obviate inlet flow separation. A lip shape or geometry which is suitable to prevent separation at the low end of the speed regime is indicated at 6 in FIG. 4. However, the shape or geometry which is suitable to prevent air flow separation at the low end of the aircrafts speed regime is unsuitable at the high end of the speed regime as exists during aircraft cruise.

The present invention provides a practical means for selectively affecting the required shape 6. As is shown in FIG. 5 the selective extension of flap 4 will force the airflow to follow a pattern which will aerodynamically form the desired lip shape for the inflow condition depicted in FIG. 4, on a lip designed for operation at less than super sonic speeds. Flap 4 is located at a predetermined distance from the leading edge of lip 3 and may be located at a predetermined radial location on the external lip.

Although depicted in the foregoing example for' a subsonic air inlet, it should be understood that the invention is also applicable to supersonic and other inlet systems where inlet flow separation could otherwise cause a deterioration in performance.

There is shown in FIG. 6 a suitable mechanism for selectively actuating the extensible flaps for diverting the airflow surrounding the inlet. The retracted position is shown in FIG. 6 and comprises flap 11 which is flushmounted with respect to exterior surface 12 of the cowling and the forward surface 13 or leading edge of the exterior side of the lip. The interior side of the forward edge of the lip l4 extends smoothly and continuously with the interior wall 15 of the inlet. An arm is secured to flap 11 and is pivotally mountedso as to permit rotation around shaft 17. Shaft 17 is suitably mounted to the cowling structure, and may for example be carried by a bearing member secured to partition 18.Arm 19 is adapted to rotate with arm 16 about shaft 17, and carries a pin 21 at its lower terminus. A hydraulic cylinder 22 is secured to a member 25' which 'is mounted on a fixed member 24. Actuation of hydraulic cylinder 22 will cause rod 23 to be retracted in the direction of arrow 20, thereby rotating arms 16 and 19.

FIG. 7 illustrates the apparatus of FIG. 6 with bydraulic cylinder 22 fully actuated (viz., member 25 fully retracted). As can be seen this will result in flap 11 being extended to a substantially perpendicular position with respect to the surface 13.

In a practical construction, a large improvement in inlet performance, as measured by increased total pressure recovery and decreased distortion, is obtained by utilization of the above-described inlet fence. Practical tests have been made demonstrating satisfactory operation atgreatly reduced distrotion levels with an inlet flow rate corresponding to an inlet throat Mach number of approximately 0.55 and a crosswind velocity of 40 knots, utilizing a continuous four inch fence located one inch aft of the inlet leading edge. The axial distance from the inlet leadingedge to the fence is fixed while the angle of the fence relative to the inlet centerline is adjustable.

Although a preferred embodiment of the device has been described, it will be understood that within the intended scope of the invention various changes may be made in the form, details, proportion and arrangement of the parts, the combination thereof and mode 'of operatibn, which generally stated consists in a device capable of carrying out the objects set forth, as disclosed and defined in the appended claims.

What is claimed is:

1. Turbine engine air inlet control apparatus, comprising:

means defining a lip surrounding the forward end of a turbine engine and providing an air inlet therefor; said air inlet having a continuous imperforate inner wall defining a path of air to the engine through said inlet;

selectively extendable and retractable fence means mounted aft of said lip in radial disposition with respect to the longitudinal axis of the engine and which, when extended, remains aft of the forward end of the inlet, to form a substantially contiguous extension of the outer surface of said forward end for diverting the airflow surrounding said inlet, said fence means deflecting the airflow exterior to said inlet into said path; and

actuator means operatively connected tosaid fence means for extending said fence means under a first operating condition and retracting said fence means under a second operating condition.

2. Apparatus as defined in claim 1 wherein said lip is substantially cylindrical and radially disposed about the axis of said engine, and said fence means is circumferentially mounted aft of said lip.

3. Apparatus as define in claim 1 including an engine nacelle carrying said lip and wherein said fence means is circumferentially mounted on and extended from said nacelle aft of said lip.

4. Apparatus as defined in claim 1 wherein said fence means comprises a plurality of hinged flaps disposed in side-by-side relationship about at least a portion of the circumference of said nacelle.

5. Apparatus as defined in claim 3 wherein said fence means comprises a ring of hinged flaps movable in unison between the extended and retracted conditions.

6. Apparatus as defined in claim 5 wherein said actuator means comprises:

a linear hydraulic actuator selectively operable between an extended position and a retracted position; and

linkage means coupling said actuator to said hinged flaps for converting the linear displacement of said hydraulic actuator to angular displacement of said flaps about the hinge pivot.

7. Apparatus as defined in claim 5 wherein each of said flaps comprises a solid rectangular member which extends substantially perpendicularly with respect to the surface of said nacelle when said actuator is in the extended position.

8. Apparatus as defined in claim 1 wherein said defining means includes:

a hollow conduit having an inlet end and surrounding said engine and carrying said lip; and

a plurality of hinged flaps movably mounted on said conduit at generally equally spaced points completely about the inlet end of said conduit carrying are directed generally radially outward peripherally about said inlet end, so as to form an outwardly extending collar thereabout.

10. Apparatus as defined in claim 9 wherein said outwardly directed flaps, when extended, are angled slightly rearward relativeto said inlet end. 

1. Turbine engine air inlet control apparatus, comprising: means defining a lip surrounding the forward end of a turbine engine and providing an air inlet therefor; said air inlet having a continuous imperforate inner wall defining a path of air to the engine through said inlet; selectively extendable and retractable fence means mounted aft of said lip in radial disposition with respect to the longitudinal axis of the engine and which, when extended, remains aft of the forward end of the inlet, to form a substantially contiguous extension of the outer surface of said forward end for diverting the airflow surrounding said inlet, said fence means deflecting the airflow exterior to said inlet into said path; and actuator means operatively connected to said fence means for extending said fence means under a first operating condition and retracting said fence means under a second operating condition.
 2. Apparatus as defined in claim 1 wherein said lip is substantially cylindrical and radially disposed about the axis of said engine, and said fence means is circumferentially mounted aft of said lip.
 3. Apparatus as define in claim 1 including an engine nacelle carrying said lip and wherein said fence means is circumferentially mounted on and extended from said nacelle aft of said lip.
 4. Apparatus as defined in claim 1 wherein said fence means comprises a plurality of hinged flaps disposed in side-by-side relationship about at least a portion of the circumference of said nacelle.
 5. Apparatus as defined in claim 3 wherein said fence means comprises a ring of hinged flaps movable in unison between the extended and retracted conditions.
 6. Apparatus as defined in claim 5 wherein said actuator means comprises: a linear hydraulic actuator selectively operable between an extended position and a retracted position; and linkage means coupling said actuator to said hinged flaps for converting the linear displacement of said hydraulic actuator to angular displacement of said flaps about the hinge pivot.
 7. Apparatus as defined in claim 5 wherein each of said flaps comprises a solid rectangular member which extends substantially perpendicularly with respect to the surface of said nacelle when said actuator is in the extended position.
 8. Apparatus as defined in claim 1 wherein said defining means includes: a hollow conduit having an inlet end and surrounding said engine and carrying said lip; and a plurality of hinged flaps movably mounted on said conduit at generally equally spaced points completely about the inlet end of said conduit carrying said lip, said flaps being selectively movable to a generally perpendicular position with respect to the surface of said conduit to form a substantially circular fluid barrier about the inlet end of said conduit.
 9. Apparatus as defined in claim 8 wherein said flaps are directed generally radially outward peripherally about said inlet end, so as to form an outwardly extending collar thereabout.
 10. Apparatus as defined in claim 9 wherein said outwardly directed flaps, when extended, are angled slightly rearward relative to said inlet end. 